Projection system

ABSTRACT

A projection system has a projection device which is used to produce a projection by emitting projection radiation, and a diaphragm device which is arranged in the beam path of the projection radiation in such a way that part of the projection is blocked out, thus causing a continuous reduction of the intensity of the projection radiation in the blocked-out part of the projection.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and hereby claims priority to PCTApplication No. PCT/DE02/04519 filed on Dec. 9, 2002 and GermanApplication No. 101 63 481.1 filed on Dec. 21, 2001, the contents ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The invention relates to a projection system with a projection deviceand a masking device.

To realize large-format image projection, a large-format image isproduced by projecting beams onto a projection screen, such as aprojection wall. In order to project a large-format image which is aslarge as possible, several individual projection systems are used,generally a large number of them, the individual projections from whichare combined to form one overall projection, the large-format imageprojection. Accordingly, the large-format image is made up of severalindividual images, generally many of them, each produced by one of theindividual projections.

TAN projection technology, TANORAMA™ POWERWALL, TANProjektionstechnologie GmbH & Co. KG. as at 17.12.2001 can be obtainedfrom http://www.tan.de. (“the TAN reference”) discloses various ways ofrealizing large-format image projections, which can be distinguished,for example, as being either an arrangement or number of individualprojection systems, or a form of overall projection.

FIG. 4 outlines the design 400 of a large-format image projection system400 with a first projector 401 and a second projector 402 together witha large-format screen 408.

The first projector 401 and the second 402 each emit projection beams inthe form of an appropriate beam or projection cone, 403 and 404respectively. The corresponding projections 405 and 406 respectively arerendered visible to a viewer by the projection beams concerned, 403 and404 respectively, being incident on the large-format screen 408.

With such large-format image projection, as illustrated by the examplein FIG. 4, overlaps arise in the transitional regions between theindividual projections or individual images, as applicable, in each ofwhich two individual projections overlap. Such an overlap region isshown, for example in FIG. 4.,407.

Such an overlap or mutual coverage is also referred to as a blend orblending region.

Because the intensities of the beams from each of the overlappingprojections or projection beams are additive, in the blending regionsbrightness errors arise which are visible and distracting to a viewer ofthe projected large-format image (blending problem).

FIG. 5 illustrates this blending problem by reference to an appropriateadditive intensity pattern 500 across a screen width 504 due to twoprojections 501 and 502 which overlap on a section 503 of the screen.

In order to achieve an (additive) intensity pattern (FIG. 3, 300) whichis uniform, correct and therefore not distracting to the viewer from twoprojections (FIG. 3, 301, 302) which overlap over a section (FIG. 3,303), the intensity of each individual projection (FIG. 3, 301, 302)must be continuously reduced (FIG. 3), starting from the beginning (FIG.3, 306) of the overlap region (FIG. 3, 303) through to an edge (FIG. 3,307) of the overlap region or of the individual projection concerned(FIG. 3, 301, 302), as applicable.

The addition of the intensities of the mutually overlapping individualprojections then gives the desired brightness distribution (FIG. 3),which is not distracting to the viewer when the large-format image isrendered visible on a screen.

FIG. 3 shows such a uniform (additive) intensity pattern 300 across ascreen width 304, from two projections 301 and 302 which overlap over asection 303 and are subject to an intensity reduction 306-307 out to theedge 307.

Depending on the projector technology used, i.e. the type of projectorsused, another problem can occur, which results in non-uniform brightnessdistributions on a projection screen.

Depending on their design, LCD projectors (in the case of LCD projectionsystems) or DLP projectors (in the case of DLP projection systems),which correspondingly use respectively LCD or DLP technology to generatean image and which are known from the TAN reference, for example, emitnot only the projection beams required for generating the image but alsoclearly visible stray beams or stray light, as applicable.

In the case of any LCD or DLP projector involved, this stray emission orstray light escapes together with an image-generating element, an LCD ora DLP module, causing intensity errors on the projection screen inaddition to the projected image.

With the systems available until now for large-format or multi-imageprojection, i.e. projection systems with at least two individualprojections combined, for example the LCD or DLP projection systemsknown from Product information on LCD or DLP projection systems, as at17.12.2001 can be obtained fromhttp://www.barco.com/projection_systems/(“the “Product Information”reference”), an intensity pattern as shown in FIG. 3 which is uniform,non-distracting and hence desired, is generated with the individualprojections concerned by electronic techniques (soft edge blending).

To achieve this with these known projection systems, based on the softedge blending technique, requires additional demanding and hence costlyelectronic modules, with additional software components for making theappropriate changes (as illustrated in FIG. 3) in the brightness orintensity pattern, as applicable, of the projections.

With the LCD or DLP projection systems, known from the ProductInformation reference, the soft edge blending technique described isboth realized in integrated form in each of the projectors used, and canalso be obtained as a supplementary solution subject to appropriatesurcharges.

With the LCD or DLP projection systems known from the ProductInformation reference, there is in addition a mutual dependence betweenthe appropriate blending control electronics for eliminating theblending problem and the projector used in each case.

Because of the technology used, the LCD or DLP projection systems knownfrom the Product Information reference can only affect the imageelements (pixels) which are contained in a projected image, so that evenwith these known projection systems the stray light problem described isnot eliminated.

Consequently, one possible object of this invention is to specify aprojection system which is simpler and cheaper to realize than the knownones, and which permits projections to be better and more efficientlyblended into each other.

SUMMARY OF THE INVENTION

The inventor proposes a projection system has a projection device, setup to create a projection by emitting a projection beam, together with amasking device which is inserted into the projection beam in such a waythat part of the projection is masked out, with the effect that acrossthe section of the projection which is masked out there is a continuousreduction in the intensity of the projection beam.

Here, the term projection refers to a multi-dimensional array of beams,created by the projection beam emitted from the projection device,generally a projection cone, with a prescribed distribution of intensityfor the projection beam.

When used in connection with the invention, the term ‘beam path’ means apath traversed by the emitted projection beam.

It follows from this that if a projection screen is introduced into thebeam path of the projection beam, which the projection beam strikes, theprojection can be rendered visible on the projection screen.

The physical fundamentals of a light beam, in particular when a beam isinterrupted at the edge of a mask, are described in Jost J. Marchesi,Handbuch der Fotografie—Band 1/Die Grundlagen {Manual ofPhotography—Vol. 1/Fundamentals} Verlag Photographie, ISBN 3723100244.The fundamentals of optical representations are described in ChristianHofmann, Die optische Abbildung, 1. Auflage {Optical representation,1^(st) Edition}, page 175, Akademische Verlagsgesellschaft Geest &Porting K.-G. Leipzig, 1988 .

The physical effect which is exploited with the invention is so-calledvignetting. The term vignetting refers to a decrease in the brightnessof an image toward the edge of the image, due to physical causes. It iscaused by peripheral beams being obscured when they pass through anaperture in a mask. As a result, not all of the beams emerging from apoint source of light reach the projection surface. Some of the beamsare shaded out. This results in a pattern of decreasing brightnesstoward the edge of the image.

One particular advantage of the invention relates to the fact that itprovides a mechanical (hardware) solution to the blending problemdescribed.

This solution, using the invention, is thus simpler and cheaper torealize than, for example, the electronic (software) solution known fromthe related art.

By comparison with this known electronic solution from the related art,the invention also has the advantage that the projection system isindependent of any particular projector type which is being used. Theprojection system can be realized with any required type of projector,for example an LCD or a DLP projector.

Furthermore, the projection system has the advantage that any alignment,i.e. adjustment of the masked-out section for the projection conditions,is substantially simplified, for example by appropriate geometricalshaping or insertion of the masking device into the beam path.

Thus it is possible, for example, by a simple change in the depth and/orposition of insertion into the beam path to change, and thus adjust, thepart of it which is masked out.

Furthermore, the projection system has the advantage that strayprojection light which escapes, such as with LCD and DLP projectors, canbe eliminated with the projection system.

For the purpose of solving the blending problem described, it is usefulthat, with a development, the section of the projection which is maskedout lies in a peripheral area of the projection. The intensity of theprojection beam can thereby be reduced in a direction toward the edge ofthe projection.

Furthermore, it is also useful for solving the blending problem that theintensity is reduced down to zero in the section of the projection whichis masked out. This makes it possible to achieve a continuous reductionin the beam intensity down to zero toward the edge of the projection.

By using an appropriate embodiment of the masking device, for example byan appropriate shape, depth and/or appropriate material, a continuousreduction in the intensity can be selectively achieved, in accordancewith a prescribable functional rule.

Because of the simplicity of realizing it, one useful rule is a linearfunction, i.e. a linear reduction of the beam intensity. Otherfunctional rules are possible, such as a logarithmic rule for the graphof the reduction in the beam intensity, or a rule which can be specifiedby a polynomial function.

The material used for the mask can be a light-tight material, such asaluminium or a metal.

Alternatively, use can be made of a non-light-tight material, such astinted plexiglass or tinted filter glass. The reduction in the intensityof the beam, and its functional form, is achieved by the filter coatingof the material and/or by changing the optical transparency of thematerial itself. The intensity graphs are then determinedcorrespondingly for each case.

The flexibility of this projection system can be increased by insertingthe masking device into the beam path in such a way that the sectionwhich is masked out can be altered. This flexibility can be realized,for example, by a simple change in the insertion depth and/or position,in each case by displacing the masking device in an appropriatedirection within the beam path.

For this purpose, a development provides an appropriate mechanicalholder with vertical and horizontal guides for the masking device ordevices, as applicable.

Because the projection system is independent of the particular projectorsystem which is used, in the developments it is possible to use anyrequired projector types, such as an LCD or a DLP projector the ProductInformation reference .

For the purpose of producing a prescribed projection pattern orprojection shape, it is helpful to use several masking devices, each ofwhich can be used to mask out part of the projection.

Here, the several masking devices can be inserted into the beam path insuch a way that the part of the projection which is not masked out hasthe prescribed shape or pattern, as applicable. An example of such ashape or pattern might be a projection cone with a rectangularcross-section.

In a development, the projection system has a projection screen forshowing the projection.

In a refinement to the projection system, a large-format projection unitis realized in such a way that at least two of the projection systemsare oriented with respect to each other in such a way that the sectionswhich are masked out from each of the projections overlap one another,at least partially.

In the overlapping section, a so-called blending (blending region)occurs, in which the intensities of the overlapping projections addtogether to form a composite total intensity.

In this case it is useful, in order to attempt to achieve a blendingregion which is as far as possible uniform and non-distracting to aviewer, if the overlap is effected in such a way that the combination ofthe intensities of the two projection beams produces an intensity with aconstant pattern in the overlapping section.

When realizing the largest possible large-format projection unit, suchas is required for presentation purposes, for example at exhibitions orsimilar demonstration events, it is useful to use or combine several ormany of the projection units, which are oriented in such a way withrespect to each other that they produce a large-format projection with aprescribable form, in particular a large-format projection cone with arectangular cross-section.

Such a large-format projection cone, when it strikes a large-formatprojection screen, then produces a regular large-format projection imagewith transitions or blending regions, between the individualprojections, which are scarcely visible to a viewer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention willbecome more apparent and more readily appreciated from the followingdescription of the preferred embodiments, taken in conjunction with theaccompanying drawings of which:

FIG. 1 is an optical hardware edge blending system (H-EBS) in accordancewith an exemplary embodiment;

FIG. 2 is a sketch of a multi-image projection with a multi-imageprojection system with an optical hardware edge blending system inaccordance with an exemplary embodiment;

FIG. 3 is a sketch showing a composite uniform intensity pattern for twoprojection systems or projections combined together with no blendingproblem;

FIG. 4 is a sketch of the construction of a multi-image projectionsystem using two projection systems combined together;

FIG. 5 is a sketch showing a composite, non-uniform intensity patternfor two projection systems combined together where there is a blendingproblem;

FIG. 6 is a sketch of the construction of a hardware edge blending(H-EBS) multi-image projection system using two H-EBS projection systemscombined together.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout.

Exemplary embodiment: an optical hardware edge blending system (H-EBS)

FIG. 6 shows the design 600 of a large-format projection system, in thiscase a two image projection system, a so-called hardware edge blending(large-format projection) system 601 (H-EBS).

The H-EBS 600 shown comprises a first H-EBS projector 601 and a secondone 602, in this case LCD projectors, together with a large-formatscreen 608.

We note for clarification that any required projector, including forexample a DLP projector, could be used for the H-EBS.

The first H-EBS projector 601 and the second one 602 each emits aprojection beam in the form of an appropriate beam or projection cone,603 and 604 respectively. Corresponding (individual) projections 605 and606 respectively are rendered visible to a viewer by the incidence ofthe projection beam concerned, 603 and 604 respectively, on thelarge-format screen 608.

Into the projection cones or beam paths 603, 604 of the H-EBS projectors601, 602 are inserted so-called H-EBS masking devices 609, 610 (FIG. 6).

The two H-EBS projectors 601 and 602 are oriented with respect to eachother in such a way that the two projections 605 and 606 are visiblebeside each other on the large-format screen 608.

In an overlap region 607, which can be modified by the H-EBS maskingdevices 609, 610, i.e. enlarged or reduced in size (see also FIG. 1),the two projections 605 and 606 cover each other mutually (blend orblending region).

FIG. 2 shows the arrangement for an individual H-EBS projection 203, forone of the two H-EBS projectors 601 and 602, from porjector 201.

FIG. 2 shows in particular, 206, the H-EBS masking device 609 or 610respectively which is inserted into the projection cone or beam path 202of the H-EBS projector 201 (see also FIG. 1).

Here, when looking in the direction of the beam path 202 the H-EBSmasking device 206 is located in front of the H-EBS projector 201 andafter the projector optics 207.

The effect of a (beam) diffraction effect 205 at a mask edge 208 of theH-EBS masking device 206, which (beam) diffraction effect 205 is knownfrom, is to achieve a virtually uniform masking out 204 of a projection203, in this case a projected image 203, out toward an edge 209 of theimage.

This has the effect that the intensity pattern 210 for an individualprojection, in this case the projection 203, is reduced 204 as shown bythe uniform (additive) intensity pattern 300 in FIG. 3 for the case oftwo projections 301 and 302 which are mutually overlapping over asection 303, and for which the intensities are reduced 306-307 outtoward their edges 307.

In a mirror-image fashion, this reduction in the intensity is effectedthrough a corresponding build-up for the second H-EBS projector 601 or602, as applicable, so that the uniform (additive) intensity pattern 300shown in FIG. 3 results over the blending region.

Thus the blending problem is solved with the H-EBS system described.

FIG. 1 shows the H-EBS masking device (which is inserted into the beampath 202 of the H-EBS projector 201), 609, 610, 206 and 100.

The H-EBS masking device 100 has a rectangular front plate 103, to whichare attached vertical guides 104 and horizontal guides 105 for holdingmasks which can be moved respectively vertically 102 or horizontally101.

Here, each of the masks 101,102 has a straight mask edge 111, with nocurve in it.

Each of the masks 101, 102 can be displaced within its guides 104 or 105respectively, and can be fixed in a desired position by lockingfacilities 106.

The front plate 103 is attached or aligned in front of the projectoroptics 207 of the H-EBS projector 201 in such a way that a horizontalaxis of symmetry 109 and a vertical axis of symmetry 110 of the frontplate 103 each corresponds with an optical axis 108 of the projectedbeam cone 202.

The horizontal and vertical arrangement of the masks 101, 102, and thefree movement of the masks 101, 102, within their guides 104, 105, makeit possible to set any desired apertures 107, in this case rectangularapertures, for letting through the projection beam.

A different shape for the masks 101, 102, or a different form for themask edges 111, would also permit transmission apertures 107 withdifferent shapes, for example curved transmission apertures 107.

This flexibility in the setting of the transmission aperture 107 permitsall the edges of a projected image to be variably masked, and therebythe blending regions flexibly adapted (adjustment).

Important advantages of the H-EBS 600 which has been described are thus:

The adaptation of the blending region or the adjustment is flexible andsimple.

By comparison with soft edge blending solutions, the cost outlay iscritically reduced.

The occurrence of stray light is eliminated.

The H-EBS 600 is independent of the type of projector used and its inputsignal sources.

The invention has been described in detail with particular reference topreferred embodiments thereof and examples, but it will be understoodthat variations and modifications can be effected within the spirit andscope if the invention.

1-13. (canceled)
 14. A projection system comprising: a projection deviceequipped for the creation of a projection by emitting a projection beamthat travels on a beam path; and a masking device, which is insertedinto the beam path of the projection beam in such a way that a sectionof the projection is masked out, and in such a way that across thesection of the projection which is masked out there is a continuousreduction in the intensity of the projection beam.
 15. The projectionsystem in accordance with claim 14, wherein the section of theprojection which is masked out is in a peripheral region of theprojection.
 16. The projection system in accordance with claim 14,wherein the intensity in the masked out section of the projection isreduced down to zero.
 17. The projection system in accordance with claim14, wherein the continuous reduction in the intensity is effected inaccordance with a prescribed functional rule .
 18. The projection systemin accordance with claim 14, wherein the continuous reduction in theintensity is effected in accordance with a linear functional rule. 19.The projection system in accordance with claim 14, wherein the maskingdevice is movable in the beam path, in such a way that the section whichis masked out can be altered.
 20. The projection system in accordancewith claim 14, wherein the projection device is an LCD or a DLPprojector.
 21. The projection system in accordance with claim 14,wherein there are a plurality of masking devices, each of which masksout a section of the projection.
 22. The projection system in accordancewith claim 20, wherein a plurality of masking devices are inserted intothe beam path in such a way to impart a predetermined shape to a sectionof the projection which is not masked out.
 23. The projection system inaccordance with claim 20, wherein a plurality of masking devices areinserted into the beam path in such a way to impart a cone shape to asection of the projection which is not masked out, the cone shape havinga rectangular cross-section.
 24. The projection system in accordancewith claim 14, further comprising a projection screen for displaying theprojection.
 25. The projection system in accordance with claim 15,wherein the intensity in the masked out section of the projection isreduced down to zero.
 26. The projection system in accordance with claim25, wherein the continuous reduction in the intensity is effected inaccordance with a linear functional rule.
 27. The projection system inaccordance with claim 26, wherein the masking device is movable in thebeam path, in such a way that the section which is masked out can bealtered.
 28. The projection system in accordance with claim 27, whereinthe projection device is an LCD or a DLP projector.
 29. The projectionsystem in accordance with claim 28, wherein there are a plurality ofmasking devices, each of which masks out a section of the projection.30. The projection system in accordance with claim 29, wherein aplurality of masking devices are inserted into the beam path in such away to impart a cone shape to a section of the projection which is notmasked out, the cone shape having a rectangular cross-section.
 31. Theprojection system in accordance with claim 30, further comprising aprojection screen for displaying the projection.
 32. A large-formatprojection unit comprising: at least two projection systems, eachequipped to create a projection by emitting a projection beam thattravels on a beam path; and at least two masking devices, each of whichis located in a beam path of a projection beam emitted a correspondingprojection device of the at least two projection devices, each maskingdevice being located such that a section of the projection created bythe corresponding projection device is masked out, and such that thereis a continuous reduction in the intensity across the section of theprojection which is masked out, wherein the at least two projectionsystems are oriented with respect to each other in such a way that themasked out sections of the projections overlap at a mutually overlappingsection.
 33. The large-format projection unit in accordance claim 32,wherein the mutually overlapping section is formed in such a way that acombination of intensities of the at least two projection beams producesan intensity with a constant pattern in the mutually overlappingsection.
 34. The large-format projection unit in accordance with claim33, wherein the projection systems are oriented in such a way withrespect to each other that they produce a large-format projection with aprescribable shape.
 35. The large-format projection unit in accordancewith claim 33, wherein the projection systems are oriented in such a waywith respect to each other that they produce a large format projectionwith a conical shape, the conical shape having a rectangular crosssection.
 36. The large-format projection unit in accordance with claim32, further comprising a large-format projection screen for displayingthe large-format projection.
 37. The large-format projection unit inaccordance with claim 35, further comprising a large-format projectionscreen for displaying the large-format projection.
 38. The projectionsystem in accordance with claim 14, wherein the masking device has anadjustable aperture which allows the projection beam to pass and has asurrounding area to block the projection beam.
 39. The projection systemin accordance with claim 38, wherein the aperture has vertical masks andhorizontal masks, at least one of the vertical masks is movable towardand away from another of the vertical masks, and at least one of thehorizontal masks is movable toward and away from another of thehorizontal masks.
 40. The large-format projection unit in accordancewith claim 32, wherein each masking device has an adjustable aperturewhich allows a projection beam to pass and has a surrounding area toblock the projection beam.
 41. The large-format projection unit inaccordance with claim 40, wherein the apertures each have vertical masksand horizontal masks, for each masking device, at least one of thevertical masks is movable toward and away from another of the verticalmasks, and for each masking device, at least one of the horizontal masksis movable toward and away from another of the horizontal masks.